Draft control



March 13, 1945. E. I JR 2,371,512

DRAFT CONTROL Filed Ahg. s, 1942 .3 Sheets-Sheet l March 13, 1945.

E. A. FIELD, JR

DRAFT CONTROL Filed Aug. 3', 1942 3 Sheets-Sheet 3 4 H; A55 44 56 I I rY t I v I W 17/10/40 if fla M.

INVENTOR.

Patented Mar. '13,

UNITED STATES, PATENT OFFICE "DRAFT coN'moL Edward A. Field, In,Mendota, Ill. Application August 3, 1942, SerialNo. 453,400

22 Claims.

This invention relates to improvements in draft controls.

The main objects of' this invention are:

First, to provide an improved automatic draft control device forcombustion heaters. stoves and the like which are entirely dependent'upon natural draft for their air supply.

.Second, to provide an automatic thermally responsive draft controlwhich is responsive to the temperature of the flue gases of the heaterto effect regulation of the draft in accordance with said temperature,appropriately increasing thedraft when the flue temperature rises anddecreasing the draft when the temperature falls.

Third, to provide a draft control of the type described, preferably foroil burning space heaters, which is effective to closely regulate thedraft of said heaters in accordance with the flue temperature, therebypreventing wasteful combustion on the one hand due to excessive draftand accumulation of soot on theother due to too low draft, and at thesame time affording requisite increased drafts for high burning rateswhich result in high fuel temperatures.

Fourth, to provide a device of the'type described which is highlysensitive in its operation, having provision for counteracting orneutralizing factors normally tending to affect the accuracy of itsoperation, and which is simple and inexpensive in its partsnotwithstanding its sensitivity.

Fifth, to provide an automatic temperature controlleddraft regulator ofthe'type described which has provision for maintaining the draft gate,in which the regulating action is exerted on the gate in a manner to beconsistent with the action of the counterweight on the gate, withresultant improved and more accurate operation. Further objects relatingtodetails and economies of the inventionwill definitely appear from thedescription to follow. The invention is defor minimum flue gastemperature and the draft control gatebeing shown in partially closedposition. I

' Fig. 2 is a viewsimilar to Fig. 1, illustrating the parts in positionfor maximum or increased temperature control, the draft'control gate inthis case being shown in fully opened position under the influence ofair pressure thereon.

Fig. 3 is an enlarged fragmentary detail view in section on a linecorresponding to line 3-3 of Fig. 1 illustrating the thermallyresponsive actuating element of the control and details of mountingthereon the smoke flue.

Fig. 4 is an enlarged fragmentary view in section on a linecorresponding to line |4 of Figs.

. 1 and 5, illustrating the structural details and the relationshipofthe parts of the control with the at values proportionate to the fluetemperature,

regardless of differences in the 'rate of increase thereof at differingtemperature ranges, for a givenfuel consumption.

Sixth, to provide an'automatic, thermally controlled device of the typedescribed including a bimetallic temperature responsive elementpositioned relative to the flue so as to lie-subject to the temperatureof the flue gases and likewise in such manner as to withstanddestructive action thereon of the sometimes exceedingly hot flue gases.Y Seventh, to provide an automatic control of the type described whichpositively limits the draft at a predetermined desired minimum value,regulating the draft proportionally to the increasingflue gastemperaturesuptoa maximum, at. V which the drattislikewise positivelylimited.

Eighth, to provide a regulator of the W9 described including a thermallyresponsive element and actuated thereby to vary the to movement of acounterweighted s; m. 9 is a tummy latter automatically positioned forminimum temperature operation.-

-Fig. 5 is a view partially broken away and in horizontal sectionfurther illustrating structural details and relationships, with thecontrol parts in the position illustrated in Figs. 1 and 4. 5

Fig. 6 is an enlarged fragmentary. view in section on a linecorresponding to line 6-6 of Fig. 2 illustrating further structuraldetails and indicating the operation of the-thermal element and parts\zonnccted thereto in solid and dotted 1 5 lines respectively.

Fig. '7 is an enlarged frag'meiitary detail view in section on a linecorresponding to line 1-1 of Fig. 5 illustrating provisionsfor-preserving accuracy and maximum sensitivity in the movements of thecontrol mechanism. Fig. 8 is a fragmentary perspective view partiallybroken away and in section illustrating a detail of the gate mountingand stop means of.-

the control.

view in section on a linewhen the temperature rises and increase thedraft when the temperature falls. In the present rearwardlytherefromparallel to said wines which act as end abutments preventing excessivelustrating a modified structure incorporating the s invention Thepresent invention relates to an automatic thermally controlled draftregulator well adapted for the regulation of oil burning space heatersof the type dependent. entirely upon natural draft for their air supply.Most such heaters can be operated at burning rates which vary from amaximum down to a minimum of only or of the maximum rate. It isdesirable that at the lower burning rates only a comparatively 5 smallamount ofair shall be supplied to the burner; however, it is a very rareoccurrence when the operator takes the trouble to alter the setting ofthe draft control of the heater for each change in the position of thefuel control valve. 20

a of a type which is dependent entirely upon nat- Manufacturers haveheretofore provided draft 4 ontrols with adjustments appropriatelymarked nd settable to correspond to similar fuel consumption markings onan oil dial, but the results neglects tochange the draft setting andsimply manipulates the oil control dial up or down to regulate the fuelsupply. This is objectionable,

for excessively high-drafts wastefuel and excessively low drafts causeaccumulation of soot.

An attempt has been made to overcome this difficulty by permanentlysetting the draft control for a rather highdraft; for example, a draftwhich is about right for a burning rate of 80% 'asvasia plied to thegate in a manner such that it counteracts to a maximum extent the torqueof the gate counterweight and thereby renders the gate least resistantto oppose the flow of air there through into the flue. It will beappreciated that a temperature sensitive mechanism of this comqpensating type is applicable to various types of draft control toautomatically regulate the set- No. 2,358,390, Sept. 19, 1944, 1illustrate the mechanism associatedwith a well-known blocking Y typecontrol. Further details of the operation of the structure chosen forillustration herein and of the principle embodied in the invention,generally considered, will become apparent as the description of thestructure proceeds. V I Referring to the drawings, the reference numetal I designates an 011" burning space heater ural draft. Thereference numeral 2 in general designates the draft control employed inthe present embodiment of this invention, which is are still notsatisfactory. The operator usually 25 housed in and supported by a pipeT, arm 3 of which is applied directlyto the smoke outlet of the heater iand serves in the manner of a smoke flue; hence it will-be referred toas such. This control device will also operam correctly if the tee islocated so as to constitute the second or third length of the flue fromthe stove, with appropriate calibration of the device for such amounting.

The outwardly projecting leg 8 of the 1 con-- or 90% of maximum, but thefact remains that as stitutes-a cylindrical draft control housing, beingthis draft is still a trifle too low for the maximum combustion rate anda great deal too high for medium or low burner settings. Most oilburning heaters are operated at a medium or low oil setdeal of fuel isneedlessly. wasted by excessive draft when the latter is set in themanner referred to.

The device of the present invention consists of a draft control'havingapplied thereto a thermally controlled apparatus which issensitive orresponsive to fine ass temperature to automatically regulate the draftsettings according to the temperature of the gases in the fine as dis-;charged from the heater. with this invention I- increase the draft whenthe temperature in the fine rises and decrease the draft when thetemperature in the fiue falls. This is a markeddeparture from theoperation of most thermally controlled regulators, which reduce thedraft invention I take advantage of the fact that fuel temperaturesincrease with higher burning rates so as to provide increased drafts forsuch higher" is operative in response to fuel temperaturesin directrelation thereto. 7

Generally stated. the device'eifects the foregoing operation by anadjustable compensating I weight appropriately connected to the draftcontrol gate, which in the illustrated embodiment isa counter-weightedone, and swingable to vary the resulting torque stresses on the gate astheprovided at .its outer end with an annular stamped, sheet-metal gateframe 5 disposed in and abutting said outer end. The framefhas a gateopening 5 therein, preferably straight sided,

' ting the majority of time, which means a great 40 provi w laterallyinwardly extending formed on the sides thereof adjacent wings 8,- and apintle rod 12 secured eccentrically to the gate and extending throughapertures in said sate flanges ll serves to provide pivot trunnions llfor the gate. The said housingwings 8 adjacent the forward end of thelatter are provided with elongated recesses II on the lower edge ofwhich gate pivoting trunnions' II are rollingly received to effect avery free frictionless journaling of the gate; while the radiallyextending side shoulder I! of, the gate frame immediately to eitherouter side of-wings 8 has-lips'or lugs l6 struck,

longitudinal or endwise movement of the gate burning rates, inasmuch asthe present. device-ootrunnions.

As illustrated in Fig. 8, the gate'flange ii on one side of the gate isslit and conformed to provide a spring stop finger I? which projectslaterally outwardly through an arcuate opening as m provided in thehousing flange or wing a.

the oppositeangular limits of said opening Ill the spring stop i1 limitsthe swinging oftlie gate at its closed and maximum open; positions. Thisis performed effectively and n silently, due to the resilient characterof stop H.

The smoke flue 3 intermediate the heater I horizontally elongatedopening It by the expe dient of slitting the side wall horizontally islocated in a position and has its torque ap- 1| and offsetting outwardlyto provide a -peir of .latter (see Figs, 2 and 5).

2371.512 parallel flanges 20 from the material thereof.

Within this opening I mount a blade-like bimetallic thermal element 2|,see Figs. 1, 2, 3 and ,6. This thermal element is fixedly secured at oneend to the side of the fluethrough its engagement by lugs l9 and 22 onthe latter. .At its other end the thermal element is securedas by therivets 22| to the laterally disposed end 23 of an angled actuating arm24, this arm being angled as shown in Fig. so that its outer end ispositioned below the housing 4 as is clearly shown in the drawings. Theportion 23 of the arm is'provided with ears 23| receiving the pivot 25carried by the flanges 20-, see Figs. 1 and 3.

The thermal element 2| is disposed with its high-expansive side on theouter side of the flue and exposed to the air in the room being heated.vThis is advantageous because of the fact that the thermal element thusdoes not become undesirably heated as is likely to be the case where itis entirely surrounded by the hot gases in the flue. A slight amount ofair leaks in around the cracks at theedges of the thermal element andtends to further cool the same. Thus an ordinary comparativelyinexpensive bimetallic bladelike member will serve my purpose, whereas,if the latter were disposed entirely within the flue and surrounded bygases, the temperature of which reaches 900 or 1000 degrees F., a veryspecial grade or design of thermal element would be called for. It isevident that' as the temperature in the flue increases the thermalelement 2| warps or bows outwardly from the position indicated in solidto dotted line position,

, correspondingly swinging the actuating arm 23,

] tion for the control, to be hereinafter referred to more fully,inwhich a predetermined pressure is exerted on the actuating arm and thethermal element-2|, and likewise a predetermined posiunder maximum fluegas temperature to which the control is responsive. This is desirablebe-- cause, if an excessive temperature should prevail in the flue forsome reason, the movement of the actuating arm 24 might be so great asto damage: the parts of the device to .be described.

At its, outer end the arm; 24 has adjustably mounted thereon anextension-arm 28, .a rivet 29 serving as a-pivotal connection. Arm 24and its extension}! are fixedly secured to one another in appropriatelyadjusted position by :ineans of a screw 30 threadedlyreceived bythe ,arm.24 and'extending through a slot 3| in ex-.

tension 28 with'its head bearing against the This permits relativeadjustment of j the actuating arm and its extension'for minimum draftpositioning o'f-th'e gate 10. Assuming that a minimum draft of .02 inchis desired, the extension 28 is appropriately set so that the partsactuated by said arm (to be Zdescribed) are positioned and exertappropriate action on the gate. Instruments are employedReferrlng-nowtoFigs. 1, 4'and 5, the control tion of maximum movement ofthe actuating arm housing 4 has depending therefrom a sheet metalsupporting frame or bracket 32 provided with an' opening to receive arm24 for free swinging movement. Bracket 32 has V notch, openings 33 inits opposite side walls receiving knife edge pivots 34 which are turnedoutwardly from a stirrup-like U shaped rocker member-35. This U shapedrocker member 35 hasrigidly secured to one of theparallel arms thereof aforwardly projecting gate compensating control arm 36 andsaid arm has asan integral part thereof a pair of out-tumed upper and lower ears 31, 38located rearwardiy of the knife edge pivots 33, said ears serving to'receive a vertical pivot pin 39. The

lower end of this pin rounded to minimize friction in its turning andrestson the cross member 40 of the rocking member 35 (see Fig. 7). Pin39 has secured thereto a laterally 'osciliatable compensating weightswing arm 4|. has a free, frictionless pivotal movement in thejournaling ears 31, 38therefor and the swing arm 4| is secured flxedlyto said pin for movement therewith. At its outer end the lever is oifsetupwardly at 42, bringing the upwardly offset portion into a plane whichincludes the pivot point of knife edges 34!. Appropriate, preferablyequal-sized, compensating weights 43, 44 are mounted on the upper andlower sides of arm portion 42 so that their center of gravity lies inthis plane.

By referenceto Fig. 5 it will be noted that compensating weight swingarm 4|, which is of sheet metal material, has its pivot pin 39 securedthereto at one inner corner thereof. Adjacent the opposite inner corner,or at least in substantially spaced relation to pin 39; arm 4| isprovided with an upwardly and forwardly turned 'ear 45 for eflecting apivotally actuating -connection between the swing arm and a link 48 bywhich the same is actuated from the actuating arm extension 28. Link 48is pivoted at its op posite end to said extension.

In effecting the aforesaid pivotal connections of link 46 to the arm 4|and actuating arm exarm extension 28. The bearings are provided withopenings 48 for the reception of the pivot, pins 50, 5|. Pin 50 extendsdownwardly through alined openings in swing arm 4| and the ear 43thereon, while pin 50 is received in an opening in the arm extension 28.The purpose'of the convex bearings 41. 48 is. to reduce the frictionbetween the parts when the actuating extension 23 is rockedhorizontally, also permitting vertical rocking or tilting mpyement ofthe arm without binding of the parts such as would detract Y armjt :andthe actuating arm extension, re-

spectively, lie in a plane ing through the pivot point of the'kni'feedges Thepurpose of this arrangement willbe hereinafter referred to.

At its outer endthe forwardly projecting gate compensatingcontrol-,arm38, which as stated is rigidly secured to. the rockingsupport 35 for vertical rocking movement therewith, has at-- tachedthereto a-connector linkl2 which extends upwardly through an opening 43in the lower part of control housing 4 and is connected at its This pinto the gate In on the rear side thereof. The point of pivotal connectionof th link 52 to bracket I53 lies in a plane extending through the gatepivot I! at an angle of approximately 70 degrees to the gate; The gateitself is provided beneath its'pivot point with a pair of counterweights8t, 85 on theouter and inner sides thereof. respectively, the weight 5being fixed and the weight a -'torque ofcounterweights 54, 65 on thegate in accordance with the temperature of the hue gases, and therebyrender the gate more resistant to opening under the external pressure ofair.

thereon as the temperature increases and less resistant to opening asthe temperature decreases. It will be understood that t combined weights54, 55 in combination with the weight of the gate 60 itself will, whenproperly adjusted, produce a predetermined closing torque effective onthe gate.

In actual manufacture, after the factory balancing operation iscompleted, the center of gravity of all of the gate carried parts willbe located in a plane passing through the gate pivot point outwardly anddownwardly at an angle of .10 degrees to the plane of the gate, and itis essentially important, in accordance with the present invention, thatthe efiect of the compensatlng provisions carried by the rockablesupportand connected to the gate shall be applied on the latter in the samemanner as the fixed counterweights 54, 55. Consequently I have madeassists upper end to a relatively short bracket I88 secured be .02.ds'the bimetallic strip as warps and bows outwardly under increasingflue gas temperature due to an increase in the fuel consumed,

actuating arm 26 is rotated counterclockwise about pin 25, as viewed inFigs. 5 and 6, from solid towarddotted line position in th latter, beingthereby effective through extension 28, link 46 and arm II to swing theweights at, 46 rear- ;vlsrdgy or in clockwise direction as viewed in Asweights #3, is approach the vertical lane passing through the knife edgepivots of the rockabie support so the torque exerted through wire link 8becomes less, due to decrease in moment arm of the weights; hence thecounteracting compensation of the fixed gate counterweights M, It isdiminished and the closing torque effective on the gate increased,requiring a greater draft to swing the same. In this connection it ispointed out that the link 52 may be attached to the front of the gateinstead of the back if the action of the compensating weight swing arm4|:

is reversed, and the same results accomplished. However. attaching thelink to the front side of the gate would require offsetting or bendingof the same to avoid being struck by the gate as v the latter is opened.Hence, it is found more the link to the rear side to the heater,likewise to stabilize the bimetallic strip 2|, I provide an internalstrut 58 extending particular provision that the links: shall .con-

nect to the gate or bracket I53 thereon in degree plane referred to.

In actual practice the gate is permitted by the stop I] and limitopening I81 to'open' about 80 degrees from its closed position andalthough the. center of gravity is located in a plane extendingdownwardly a slight degree when the gate is closed or in verticalposition, nevertheless throughout the greater part of the swing ormovement of the gate the center of gravity of the combined gate partsmoves upwardly and over toward the vertical plane of the gate, therebeing the 70- only about 20 degrees of gate movement (at the time thelatter starts to open) when the center of gravity movesaway from thevertical plane of the gate. This is consistent with principles which'Ihave found to be sound.

position for minimum draft and temperature control, as illustrated inFigs. 1, 4 and 5, a torque will be exerted on the rocking support 35 ina clockwise direction as viewed in Fig. 5, which is of sumcientmagnitude to oflsetor neutralize most of the aforesaid counterweightclosing torque on the gate, leaving a net difference of only the amountnecessary to close the gate across between the two sides of the T. Also,in order to prevent the bimetallic strip from bein unduly influenced bycool air entering and passing through the draft control housing 1, whichair sometimes tends to eddy back into the flue toward the heater l, Iprovide deflecting louvers it at the inner corner of housing 4 adjacentits union with the flue portion of the T. In the illustrated examplethese louvers consist of curved bands of metal arranged overlapping insuch a manner as to tend to direct the air flow towards the chimneyinstead of striking the back side of the 1' and swirling in alldirections; These louvers also assist in preventing disposition of sootin the draft control, but the primary purpose thereof as regards thepresent invention is to prevent the cold air from contacting orinfluencing or affecting the inner side of the thermal element. If thisoccurs, then on a day when the gate IQ has to be opened quite wide, ason a clear cold day, much more air will be passed into the pipe thanwould be the case on" a warmer day, and consequently the most desirableactionof the control device will not be had. 7

Referring to Figs. 4 and 5, it will be noted that the link actuatingcompensating arm 33 on the rocker support "has an added piece 51'affixed thereto constituting a counterbalance or counterweight for therocking assembly. This weight is positioned on the arm 86 tocounterbalance the weight of the other parts of the rocking assembly, sothat when the compensating weights", .44 are removed and swing arm 4| isin the forwardminimum draft position of Fig. 5 thecombinedparts aresubstantially 'in'balance, with their combined center of gravitycoincident with theaxis of the rocker assembly, 1. e., on a line passingthrough the knife edges 3 by which said asscmblyispivoted.

While the rocking assembly does not swing' more than five or six degreesto either side of the horizontal position of arm 30 as shown in againstthe desired minimum draft, assumed to 1 Pig. 4, yet if thecombinedcenter of. gravity were .6, so that link 46 is thrust underbearings 41,

n ider ly above or below the pivotal axis of the assembly, then, as therocking support 35 rocked and the center of ravity was shifted overclose to the vertical plane of the axis, the torque developed would varyconsiderably. To avoid this I have provided that the compensatingweights 43, 44 are of the same size and weight and are disposed oneabove and one below the vertical offset end 42 of lever arm 4|. Thisassures that the plane in which the outer portion of the arm swings. andthe center of mass of the two weights will pass through the pivotal axisof has been pointed disposes the'end the rocker assembly, since, as out,the ofiset in swing arm 4| thereof in a plane passing through the pivotpoint of knife edges 34. The combined center of gravity of weights 43,44 and arm It always rocks through the same part of a vertical arc,regardless of the lateral position of the compensating weight swing arm4|.

If the temperature of the flue gas increases, indicating the need for agreater draft for perfect combustion, the bimetallic strip 2| bowsoutwardly from solid lineposition of Fig. 6 toward the dotted lineposition, rocking the actuatin arm 24 which is rigidly secured theretoin counterclockwise direction as viewed in Figs. 5 and compression tothe left in Fig. 5 and thereby pivoting swing arm 4| in clockwisedirection as viewed in Fig. 5. This thermally derived force istransmiitted accurate-- ly and proportionately regardless of theposition of the gate l0, and hence of therocking assembly on which theforce transmission link 46 is carried, due to the provision'of therounded pivotal connection to actuating arm extension 23 and theswing-arm 4|. The holes in said link receiving the pivot pins large sothat the rocker assembly can swing up or down 8 or 10 degrees withoutany appreciable detract from thebinding action suchas would accuracy orsensitivity of the device.

I have pointed out above the aforesaid link pivotal points or bearingsare in a plane passing through the pivotal axis of the rocking assemblyat knife edges 34 (see Fig. '7). It will be further noted by referenceto this; last figure that the point where the link is pivoted to theactuating arm extension 28 is very close to said rocker assembly axis atknife edges 34, hence, as. arm 24 and extension 28 swing to the rear incompensating to provide increased draft, the link pivot to extension 28passes by a short movementthrough the rocker assembly axis and beyondthe same a slight distance on the other side thereof. By making thedistance traversed by the pivot link connection on either side of therocker assembly axis comparatively small, the accuracy 'vice isconsiderably contributed to. If link 48 of the deing arm 24 andextension 28 thereof. The latter should, and in the arrangement asdescribed does, only function to position the compensating weightstemperature so that said compensating weight may accurately exert itsproportional compensating effect on the counterweighted gate.

As compensating weights 43, 44 are swung to the rear in clockwisedirection under the. influence of increasing flue temperature, theybecome, as stated, decreasingly effective in their ability to offset theaction of the main gate counterweights 54, 55, with resultant increasein the resistance of gate iii to swinging and production of a higherdraft for the heater I. This swinging movement continues to a maximumdraft position so far as the control is concerned, in which actuatingarm 24 strikes the stop 21-. Further excessive increase in thetemperature due to an abnormal combustion condition is thereafterineffective in moving the compensating weights, with attendantpossible-damage to the more delicate parts of the device.

It is a well-known fact that operating characteristics of differentstoves are not the same. with some stoves or heaters the rise in fluegas temperatures as the fuel consumption is increased, is approximatelya straight line, while with others it is in the form of a curve. Thismay be allowed for in the present device by changing the point ofattachment ofthe link 48 to the swing arm 4 I, also by changing theposition of the said swin 48 on the link at the points of its and thenumber of so, an are sufficiently were attached to extension 28 at arelatively great the link pivot to arm extension 28 is closely adjacentthe rocker assembly pivot axis in any position of said extension thereis substantially no horizontal swinging of the arm 4| due to thevertical rock of the rocking assembly.'- In otherwords, said assembly isrocked'only in response to -preponderating pressure of air on gaterather than the possibility of rocking the same accidentally due to themovement of the'actuatarm at its initial starting position for lowdraft, using the adjustment described above. Thus the swing arm can bemade to rotate through different parts of the are for different stovesor heaters,

be varied. Also, if the size ofjthe weights 43, 44 is changed the torquedeveloped can be made to conform approximately to-the requirements ofpractically anyv stove.

,As will be apparent from an inspection of Fig. 5, the change in torqueexerted by weights 48, 44 is relatively small as the arm 4| first startsto swing away from its position in that figure,

there being little movement toward the rocking assembly axis, but as thearm 4| approaches its other extreme position the change in torque isquite rapid for each degree of swing. This onsets the fact that flue gastemperatures rise more as the fuel feed is increased from alow than istrue after the stove is already operating at a fairly high burning rate.To illustrate this, in a given type heater, if the oil feed is increasedfrom '1 cc. per minute to 14 cc. per minute, the flue gas temperaturemay increase asmuch as 200 degrees F., but when the oil feed is changeda similar amount from 21 cc. to 28 cc. per minute the flue gastemperature may increase 'only degrees F; Therefore, it will beappreciated that my control is sensitive to this nonlinear relation fuelfeed to flue temperature to in-' sure the supply of adequate yet notexcessive air to. the heater, in proportion with the air requirementsfor most eiilcient combustion. Under the conditions stated the draft atthe lower rate of fuel consumption is maintained proportionately low andat the high rate of consumption is maintained proportionately high,notwithstanding the fact that the ultimate adjustment of the-mechanismitself, i. e., the angular swing of arm 4|, is linearly responsive .inproportion to the changes in flue gas temperatures.

mm. 10 Ihave illustrated a modified'adaw' tation of the invention,similar tothe foregoing- 43, .44 in accordance with the flue gas degreesof rotation may also in all respects, save that the actuating arm 2Q (orappropriate adjustable extension thereon, not shown) is effective on thecompensating weight swing arm 4| by a camming action instead of thelinkage arrangement illustrated in the preceding figures. In thisembodiment arm 24 is provided with 9. lug or pin 60 engaging the camslot 6| which is provided in the swing arm ii in spaced' relation to itspivot 39. The arms N and 6! are swing from solid to dotted line positionin the manner illustrated, as the bimetallic strip 2! bows underincreasing flue gas temperature and reversely underdecreasing'temperature. by cam engagement of lug Bil with opposite sidesof the cam slot 8| as will be readily appreciated.

Further modifications incorporating the principles discussed at lengthabove will readily sug- -gest themselves to those skilled in the art.Thus different forms of thermally responsive element connected to therocking support 35 in appropriate fashion will procure a similar result,if the broad concepts explained above are adhered to. Similarly variousalternative methods of. applyassume control member resisting movementthereof, a

compensating swing arm pivoted, on said rocker member for lateralswinging movement at right angles to the plane of rocking movement ofthe a member, a compensating weight carried by said swing arm, thecenter of gravity of the swing arm and weight traveling laterally in. aplane including the pivotal axisof said rocker member to alter themoment arm of said compensating weight and thereby vary the torque ofsaid rocker memher, and means forvariably positioning said swing arm andcompensating weight in accord ance with the temperature in said flue tothereby regulate the bias on said draft control member, comprising athermally responsive bimetallic element positioned adjacent said fineand subject to the flue. gas temperature therein, an actuating armpivoted adjacent said flue, said element being secured at one endthereof to the flue and at thermally controlled devices which operateinversely to reduce draft upon increase in the flue gas temperatures, mydevice maintains a direct proportion therebetween, within certaindefinite predetermined chosen maximum and minimum draft conditionswhichmay be selected as dethe other end thereof to said actuating arm,whereby movement of said element in response to changes in the fluetemperature results in swinging of the actuating arm around its pivot,and a link eccentrically pivoted to said swing arm and pivoted to thefree end of said actuating arm for actuation of the swing arm andcompensating weight in response to thermal changes in the fine, saidlink pivot points lying in-a plane in cluding the pivotal axis of therocker member. 2. An automatic, thermally responsive draft controldevice, comprising in combination with a heater flue, a draft controlhousing communicating with said flue provided with a pivoted draftcontrol member subject to air pressure externally of the housing andnormally biased to resist movement under said pressure, a rocker memberpivotally supported for vertical rocking movement and operativeiyconnected .to said draft control member whereby rocking torque of saidso rocker member is effective-to modify the bias on sired uponinstallation. 0! course, high buming rates produce high fueltemperatures and my device takes advantage of this fact to provideincreased drafts for the higher burning rates, with the resultantimproved emciency, since it is responsive to the fiue temperature. Useshows that a very close correspondence exists in the proportion betweenfuel consumption and the flue gas temperature on the one hand and thedraft as regulated by my device on the other hand, with highly desirablecombustion indeed under all operating conditions as reflected by C02analysis. I have illustrated and described my invention in embodimentswhich have been found to be very satisfactory in operation. I have notattempted to illustrate or describe other embodiments or adaptationswhich I contemplate as it is believed this disclosure will enable thoseskilled in the art to embody the invention as may be desired. v i

- Having thus described the invention what I claimvas new and desire tosecure-by Letters Patout is: I

1. An automatic responsive draft said control member resisting movementthereof.

a compensating swing arm pivoted on said rocker member for lateralswinging movement at right angles to the plane of rocking movement ofthe member, a compensating weight carried by said swing arm for lateralmovement to alter the moment arm. of said compensating weight andthereby vary the torque of saidrocker member.

and-means'for variably positioning said swing arm and compensatingweight in accordance with the temperature in said flue to therebyregulate the bias on said draft control member comprising a thermallyresponsive element positioned adjacent said flue and subject to the fluegas temperature therein,, an actuating arm pivoted adjacent said flue,said element being secured to said actuating arm whereby movement ofsaid element in response to changes in the flue tem-;

perature results in swinging of the actuating arm around its pivot, anda link eccentrically pivoted to said swing armm'nd pivoted to the freeend '01 said actuating arm foiactuation of the swing control devicecomprising incombination with a heater flue, a draftcontrol housingcommunicat ing'with said flue provided with-a pivoted draftcontrolmember subject to air pressureextemally of the housing andnormally biased to resist movement under said pressure, a rocker membersubject to torque tending to resist ment of the gate in response toexternal air prespivotally supported for vertical rocking movement andoperatively connected to said draft control member whereby rockingtorque of said rocker member is effective to modify the bias on said armandcompensating'weight in response to thermal changes in the flue.

3. In combination with a heater smoke flue dischar combustion gases, adraft control housing cornmunicating'therewith at one end and at itsother end provided with an air admission opening and a counter-weightedgateeccentrically pivoted in the opening. said gate being normalyopening movesure thereonra thermally responsive element located adjacentand subject to the temperature in the flue, a pivoted actuating armconnected earner: I 7

to said element and pivotally mama thereby in resopnse to thermallyinduced movement of the latter, a rocker member mounted for verticalswinging movement and operatively connectrocking torque of said ed tosaid gate whereby member is transmitted to the gate to alter the torquenormally effective thereoma swing arm pivoted on said rocker memberhaving a compensating weight thereon, a link pivotally connectedeccentrically to said swing and actuating arms respectively to transmitthermally induced movement of the latter to the former and thereby varythe moment arm of the compensating weight relative to the pivotal axisthe rocker member, said compensating weight,'depending on its moment armrelative to theepivotal axis of said rocker member beingeffectivethrough said rocker member and connection thereof to the gate to exertgreater or less compensating e!- iect on the torque on the gate tendingto resist movement-of the latter, andmeans to-limit the movement-of saidactuating arm at opposite extriemes thereof.

4. In combination with-a heater smoke flue discharging combustion gases,of a draft control housing communicating therewith atone end and at itsother end provided with an air admission opening and a counterweightedgate eccentrically pivoted in the opening, said gate being nor mallysubject to torque tending to resist opening movement of the gate inresponse-to external air pressure thereon, a thermally responsiveelement located adjacent and subject to the temperature in the flue, aivoted actuating arm connected to said element and pivotally actuatedthereby in response to thermally inducedmovement of the latter, a rockermember ,mounted for vertical swinging movement and operatively connectedto said gate whereby rocking torque of said mom-.-

her is transmitted to the gate to alter the torque normally efi'ectivethereon, a swing arm pivoted on said rocker member having a compensatingweight thereon, means operatively connecting said swing and actuatingarms respectively to transmit thermally induced movement of the latterto the former and thereby vary the moment arm of the compensating weightrelative to the pivotal axis of the rocker member, said com'-. pensatingweight, depending on its moment arm relative to the pivotal axis of saidrocker ,mem-

ber', being effective through said rocker member and connection thereofto the gate to exert greater or less compensating effect on the torqueof the gate tending to resist movement of the latter.

' 5. In an automatic thermally responsive draft control device, invcombination with a heater smoke flue adapted to be traversed by combus-etion gases, a draft control housing communicating therewith at one endand at its other end provided with an air admission opening and acounterweighted gate eccentrioally pivoted'inthe opening, said gatebeing normally subject to torque tending to resist opening movement ofthe gate in response to external air. pressure thereon, a thermallyresponsive element subject to the temperature in the flue between saidcontrol housing and the heater to which the flue is saidmembe'r istransmitted the gate to alter the torque normally eflective thereon, aswing arm pivoted on said rocker member having a axis of the rockermember,- and' a link pivotally connected eccentrically to said swing andactuating arms respectively to transmit thermally induced movement ofthe latter to the former and thereby vary the moment arm oi thecompensating weight relative to the pivotal axis of the rocker member,the pivotal points of connection of said link to said arms lying in a,plane passing through the ivotal axis of the rockable member, saidcompensating weight, depending on its moment arm relative to the pivotalaxis of said rocker member, being effective through said rocker memberand connection thereof to the gate to exert greater or less compensatingeffect on the torque onthe gate tending to resist movement. of thelatter, and means to limit the movement of said actuating arm atopposite extremes thereof. l r

6. In combination -with afheater smoke flue discharging combustiongases, a draft control housing communicating therewith 1 at one end andat its other'end provided with an air admission opening and acounterweighted gate eccentrically pivoted in the opening, said gatebeing. normally subject to torque tending to resist opening, movement ofthe gate in response to external air pressure thereon, a thermallyrespon'sive element located adjacent and subject to the temperature inthe flue, an actuating member connected to said element and actuatedthereby in response to thermally induced, movement of the latter, arocker member mounted for vertical swinging movement andoperativelyconnected to said gate whereby rocking torque of said memberis transmitted to the gate to alter the torque normally efiectivethereon, a compensating weight shiftably mounted eccentrically a pivotalaxis of the rocker member, said compensating weight, depending on itsmoment arm relative to the pivotal axis of said rocker member, beingeffective through said rocker member and connection thereof to exertgreater or less compensating effect on the torque on the' gate tendingto resist movement of the latter.

7. In combination with a heater smoke flue I discharging combustiongases, a draft control connected, apivoted actuating arm connectedtosaid element and pivotally actuated thereby in response to thermallyinduced movement of the latter, a rocker member mounted for verticalswinging movement and operatively connected to said gate at a point in aplane including the gatepivotal axis and the center of gravity of thecounterweighted gate, whereby rocking torque of housing communicatingtherewith at one end and at its other end provided with an air admissionopening and a counterweighted gate eccentrically pivoted in the opening,said gate being normally subject to torque tending to'resist openingmovement of the gate in response to external air pressure thereon, athermally responsive element located adjacent and subject to thetemperature in the flue, an actuating member connected to' said elementand" actuated thereby in response to' thermally induced movement of thelatter, a rocker member operatively connected to said gate wherebyrocking torque of said member is transmitted to the gate to alter thetorque normally efiective thereon, a compensating weightshiftably'mounted on said rocking member, and means operativelyconnecting ,said weight to said actuating element to transmitthermallyinduced movement of the latter to the former and therebyvary-the moment arm of the compensating weight relative to the pivotalaxis ofthe rocker member, said compensating weight, depending on itsmoment arm relative to the pivotal axis of said rocker. member, beingeiiective through said rocker member and connection thereof to exertgreater or less compensating efiect on the torque on-the gate tending toresist movement of the latter.

8, An automatic thermally responsive draft control device comprising, incombination with a heater flue, a draft control housing communicatheaterflue, a draft control housing communicating with-said flue provided witha swingable draft control member subjectto air pressure externally ingwith said flue provided with a rotatable draft control member subject'toair pressure externally of the housing and normally biased to resistrotative movement under said pressure, a rocker' member mounted forvertical rocking movement and operatively connected to said draftcontrol member so that vertical movement of said rocker member isefiective to modify the bias on said control member resisting movementthereof,' a

compensating weight swing arm pivoted on said rocker member for lateralswinging movement of'the member, a compensating weight carried by saidswing arm, the swing arm and weight swinging laterallyto alter themoment arm of said.

compensating weight on the rocker member and thereby vary the torqueexerted by said rocker "member, and means for variably positioning saidswing arm and compensating weight in accordance with the temperature insaid flue to thereby regulate the biason said draft control member,comprising a thermally responsive element subjectv to the temperature ofgases which are discharged to the flue, actuating means connected tosaid element for operation thereby in mponse to changes in t e flue gastempera-)- ture, means operatively connecting said actuating means tosaid swing arm for swinging movement of the compensating weight inresponse to thermal changes in the flue gas, therebyaltering the torqueapplicable through said rocker membeer on said draft control member.

' .9. An automatic thermally responsive. draft control devicecomprising, in combination with a heater flue, a draft control housingcommunie eating with said flue provided with a rotatable draft controlmember subject to air pressure exresist rotative movement under saidpressure; a

' rocker member operatively. connected-to said draft control member sothatvertical movement of said rocker member is efiective to modify thebias onsaid control member resisting movement thereof, a compensatingweight shiftablymounted on .said rocker member to alter the I moment ofsaid compensating weight on the rocker member and therebyvarythe torqueexthe closing bias on the control member in accordance with thetemperature in said flue, comprising a thermally responsive elementsubject to the temperature of the gases which are discharged to "theflue, an actuating member mounted adjacent said flue and connected tosaid element for actuation thereby upon operation of the element inresponse to changes in the flue gas temperature, and means operativelyconnecting said actuating member to said weight for shifting of thecompensating weight in response to thermal changes in the flue gas.

11. An automatic thermally responsive draft control device comprising incombination with a smoke flue, a draft control housing communicatingwith the flue, means to prevent swirling of ternally of the housing andnormally biased to 50 erted by said rocker member, and means forvariably positioning said compensating weight in accordance with thetemperature in said flue to thereby regulate the bias. on said draftcontrol member, comprising a thermallyresponsive element subject to thetemperature of the gases which are discharged to the flue, actuatingmeans connected to said element for operation thereby in response tochanges in the flue-gas temperatuating means to said compensating weightinf response to thermal chang'esin the flue gas, thereby altering thetorque applicable through said rocker member on said draft control mamber.

10. automatic thermally. responsive draft air entering said housing intosaid flue in the direction'of the heater attached thereto, a draftcontrol member pivoted in said housing subject to external air pressure,a thermally responsive bimetailic element disposed in an opening in saidflue between the heater and housing and fixedly secured at one end tothe flue, a pivoted actuating arm operatively connected to the other endof said element for swinging movement in response to thermal changes inthe latter, asupport so cured to said housing, a compensating assemblycomprising a rocker member pivoted on said support for vertical rockingmovement having a compensating arm connected by a link to said draftcontrol member, said rocker member being pro-- vided with a compensatingweight positioiiable variably relative to the axis ofsthe rocker member,and means connecting said weig'htto said actuating arm for shifting ofthe weight-relative to the axis of rotation of the rocker member inresponse to changes in temperature in said flue.

12. In an automatic thermally responsive draft regulatonin' combinationwith a flue member dis-' charging products of combustion, a draftcontrol device having adraft passageway communicating with the member,said device being provided with a draft control element having openingand closing movements in said passageway for regulating the flow of airtherethrough to the member, said ture', andmeans operatively connectingsaid acdraft control element being mounted to be opened by excess ofoutside atmospheric pressure over inside flue pressure, means forresisting openingmovement of said control element, said member havinganopening therein inadyance of the draft rol connection thereto,af**"blade-like thermany responsive element located in said opening andsecured at tone end to the member so as to be subject onone Side thereof:to the temperature internally of the member and on the other side tothe temperature externally of the member, and

control device, comprising in combination with a 78 for' resisting meansoperatively connecting the other end of.

said thermally responsiveelement-tosaid means opening movement of saiddraft tiv to increase the resistance of said control element draftcontrol element toopeningmovement in accordance with increase in thetemperature in mounted end of said thermal responsive element whereby Ythe arm is swung on its pivot withthe flexing ofv said member eflectiveon said thermallyresponsive element,

7 1a. In an automatic thermally responsive draft regulator for acombustion heater, a smoke flue having an opening in the wall thereof, adraft control device provided with a draft control member regulating theheater draft, a thermally responsive element located in said opening inthe wall of the smoke flue of the heater, said thermally responsivelement being a blade-like structure disposed to constitute a closuremeans for said opening, saidelement being subject directly on one sidethereof to the temperature of the flue gases internally or the flue andon the other side to the temperature of the atmosphere externallyof theflue, and means operativelyconnecting said thermally responsive elementto said draft control memberto regulate said member in accordance withthe temperature in said flue eflecon said element. 4. An automaticthermally responsive draft control device comprising, incombustion witha ing with the flue, means to prevent swirling of air entering saidhousing into trol member pivoted in said housing, said draft controlmember to be' opened by excess of outside said flue and comprising agate sociated with over inside flue pressure and provided with normalclosing torque means, said smoke-flue havingan opening in the wallthereof in advance of the inlet from said gate, a blade-like thermalresponsive element disposed in said opening and subject on its innerside to the temperature. within the flue and on its outer side to thetemperature without the flue, there being air inlet spaces at thelongitudinal edges of said thermal responsive element, said at one endthereof, an arm said-thermal responsive element is swung on its pivotother end 'of mounted counterweight operatively assaid gate, andoperating connections for said arm to said shiftable weight.

16. In combination with charging combustion gases, a drart controlassoelated with said device and comprising a gate shifts-151$ mounted tobe opened by excess of outside atmospheric pressure over inside fluepressure andprovided with closing torque means, said device having anopening therein in advance of the inlet said gate, a thermal responsiveelement dis osed in said opening and subject on one side to thetemperature within the device and on its other side A to the temperaturewithout.- said thermal res ve element being secured to said device atone end thereof, an arm pivotally said flue in the direction of theheater attached thereto, a draft conthermal responsive element beingsecured tothe said flue Y pivotaily mounted on said flue and secured tothe a heater device dis smoke flue, a draft control housingcofnmunicatmeans to increase the closing on said device and secured totheother' said thermal responsive connections for said arm torque meanswhereby the closing torque'is varied as the temperature within andwithout the device is varied. i I i 1'7. In combination with the smokeflue of an oil burning apparatus, a draft control associated with saidflue and comprising a gate mounted to be opened by excess of outsideatmospheric pressure over inside flue pressure and provided with closingtorque means, said smoke flue having an opening in the wall thereof, athermal responsive element disposed in said opening. and subject on on-side to the temperature within'the flue and onits other side to thetemperature without the flue, and operating connections for said thermalresponsive element to said gate closing torque torque on the gate as.the flue temperature rises, whereby differences between outsideatmospheric pressure and inside flue pressure, on sa'd gate, may effectautomatic opening andiclosing temperatures of the flue gases as well asat rela- 1 tively' low temperatures of said'gases.

, disposed'in said opening to be subject on its inner Z.

, outerside to the 18. In combination with'the flue of a combustionapparatus, a draft control associated therewith and comprising a housingopening tothe flue, a gate swingably be opened by excess sure overinside flue press e-and provided with variable closing torque the saidflue having an opening therein, athermal responsive element side to thetemperaturewithin the flueand on its temperature without the flue,

delivery and of said houslouvers disposed at the therethrough rearing to.deflect air passing jwardly in" the flue and away from the said thermal responsive element, and operating connectionsfor said thermal;responsive element to :said

variable-closing torque means for said gate, 7 19. In combination [withthe flue of a'combustion apparatus, a draft control associated ther Iwith and comprising a. gate mounted to be opened vfltlrthe flexing of'said' thermal responsive element, a

' outer side to the 'inside' flue pressure posed in said openin side tothe temperature outer side to the temperature-without the flue, amovably mounted weight operatively connected:

by excess of outside ing therein, a thermal responsive element distowithin the flue and on its to the gate, and operating connections forsaid thermal responsive element-to'saidweight toincrease the closingtorque on the gate as the flue temperature rises, whereby differencesbetween outside atmospheric pressure and inside flue pressure, on saidgate, may effect automatic opening and closing of the-same at relativelyhigh temperatures of the flue gases as well as at relatively lowtemperatures of said gases. 4 20. In combination with the flue ofa-combustion apparatus, a draftcontrol associated therewith andcomprising by excess of outside atmospheric pressure over inside fluepressure and, torque means including a weight, said flue having anopening therein, a disposed in said opening to be subject on its innerside to the'temperature within the-flue and on its and operatingconnections for said thermal reelement, and operating to saidgate-closingof the same at relatively high mounted inysaid housing to vof outside atmospheric presatmospheric pressure over and provided withnormal. closing torque means, said fluehaving anopenbe subject onitsinner a gate mounted to be. opened provided with closing thermalresponsive element temperature without the flue,

sponsive element to said weight to increase the closing torque on thegate as the flue temperature rises, whereby diflerences between outsideatmospheric pressure and insid flue pressure, on said gate, may effectautomatic opening and closing of the same at relatively hightemperatures of the flue gases as well as at relatively low temperaturesof said gases.

21.. In combination with a combustion apparatus discharging Products ofcombustion, a draft control associated therewith and comprising a gatemounted to be opened by excess of outside atmospheric pressure overinside flue pressure and atmospheric pressure and inside flue pressure,on

said gate, may effect automatic'opening and closing of the same atrelatively high temperatures of the flue gases as-well as at relativelylow temperatures of said gases.

22. In an automatic thermally responsive draft control, in combinationwith a smoke flue, a draft control device having a passageway to saidflue,

, a gate pivotally mounted in said passageway to be increasing anddecreasing the closing torque on said gate, thermally controlled meansdisposed to be subject to the temperature ofthe gases passing throughthe smoke flue, said thermally controlled means being conneeted to saidcompensating weight to move the same towards and-from said pivotal axis,whereby differences between outside atmospheric pressure and inside fluepressure, on said gate, may effect automatic opening and closing of thesame at relatively high temperatures of the flue gases as well as atrelatively low temperatures of said gases.

- EDWARD A. FIELD, JR. 1

